1. Field
Some example embodiments relate to a gallium nitride (GaN) film structure, a method of fabricating the GaN film structure, and/or a semiconductor device including the GaN film structure. For example, some example embodiments relate to a method of fabricating a GaN thin layer, by which a high-quality GaN layer may be grown on a large-area substrate using an electrode layer suspended above a substrate, a GaN film structure fabricated using the same, and a semiconductor device including the GaN film structure.
2. Description of the Related Art
Gallium nitride (GaN) may be a Group III-V compound semiconductor material. In general, a GaN-based semiconductor device may have a higher breakdown voltage and higher high-temperature stability than semiconductor devices formed of other compound semiconductor materials. Thus, a GaN-based semiconductor device has widely been employed in high-power apparatuses or apparatuses susceptible to high temperatures. Also, GaN has been utilized in semiconductor laser devices and light-emitting diode (LED) devices due to its desirable light emission effect. However, crystallizing GaN may be relatively difficult.
GaN may be fabricated on a heterogeneous substrate having a hexagonal crystal system, such as a sapphire (Al2O3) or silicon carbide (SiC) substrate, using a metal organic chemical vapor deposition (MOCVD), a molecular beam epitaxy (MBE), or a hydride vapor phase epitaxy (HVPE) method. However, since a relatively small sized Al2O3 or SiC substrate has been used, e.g., about 2 inches, previously, producing GaN crystals in large quantities may be difficult, thereby precluding a reduction in the fabrication cost of GaN crystals. Despite a recent growing tendency to convert 2-inch substrates into 4-inch substrates, the 4-inch substrates are still expensive. Furthermore, when GaN crystals are grown to a relatively large area, a substrate may be easily deformed due to a difference in coefficient of thermal expansion between the substrate and GaN, thus precluding formation of the GaN crystals.
In another method, growing GaN crystals on, for example, a silicon (Si) substrate, has been proposed. However, since there are big differences in the lattice constant and coefficient of thermal expansion between Si and GaN, the grown GaN crystals may have a considerably high crystal defect density and suffer from a frequent occurrence of cracks. When a relatively inexpensive glass substrate is used as a substrate, since the substrate may be greatly deformed due to a high growth temperature above about 1000° C., growing a GaN layer on an amorphous substrate, such as the glass substrate, may be extremely difficult.